0
selected
-
1.
1H NMR characterization of chitin tetrasaccharide in binary H2O:DMSO solution: Evidence for anomeric end-effect propagation.
Li, K, Green, AR, Dinges, MM, Larive, CK
International journal of biological macromolecules. 2019;:744-749
Abstract
Chitin oligosaccharides, composed of homogeneous β(1 → 4)-linked N-acetyl-D-glucosamine (GlcNAc) sequences, is a well-known elicitor of plant immune defense, and also occur as structural elements of chitosan and nodulation (Nod) factor. Detailed microstructure characterization is required for understanding the function mode of these bioactive molecules. Herein, experimental conditions for detection and elucidation of the 1H NMR resonances of amide groups in chitin oligosaccharides are presented. The binary mixture of 70% H2O: 30% DMSO‑d6 was found to be the optimal solvent for amide proton measurements in homogeneous GlcNAc sequences, facilitating differentiation of the local chemical microenvironments of all four amide groups of the chitin tetrasaccharide. Experimental evidence that anomeric end-effect triggers amide proton resonance differentiation at the adjacent residue has potential to provide important insights into the solution structure of chitin and other amino sugars containing GlcNAc sequences.
-
2.
Microbial effectors and the role of water and sugar in the infection battle ground.
El Kasmi, F, Horvath, D, Lahaye, T
Current opinion in plant biology. 2018;:98-107
Abstract
Phytopathogenic microbes multiply in the apoplast-a plant's intercellular spaces-of infected plants, and hence their success relies on the conditions in this habitat. Despite being extracellular parasites, most microbes translocate effectors into host cells that promote disease by acting inside cells. Initial studies suggested that effectors act predominantly as suppressors of plant immunity. These pioneering studies were trend-setting, causing a strong bias in the functional investigation of effectors. Yet, recent studies on bacterial model pathogens have identified effectors that promote disease by causing either increased sugar or water levels in the apoplast. These studies are likely to initiate a new era of effector research that will clarify the disease-promoting rather than defense-suppressing function of effectors, a molecular rather than genetic distinction.
-
3.
The Role of Signaling via Aqueous Pore Formation in Resistance Responses to Amphotericin B.
Cohen, BE
Antimicrobial agents and chemotherapy. 2016;(9):5122-9
-
-
Free full text
-
Abstract
Drug resistance studies have played an important role in the validation of antibiotic targets. In the case of the polyene antibiotic amphotericin B (AmB), such studies have demonstrated the essential role that depletion of ergosterol plays in the development of AmB-resistant (AmB-R) organisms. However, AmB-R strains also occur in fungi and parasitic protozoa that maintain a normal level of ergosterol at the plasma membrane. Here, I review evidence that shows not only that there is increased protection against the deleterious consequences of AmB-induced ion leakage across the membrane in these resistant pathogens but also that a set of events are activated that block the cell signaling responses that trigger the oxidative damage produced by the antibiotic. Such signaling events appear to be the consequence of a membrane-thinning effect that is exerted upon lipid-anchored Ras proteins by the aqueous pores formed by AmB. A similar membrane disturbance effect may also explain the activity of AmB on mammalian cells containing Toll-like receptors. These resistance mechanisms expand our current understanding of the role that the formation of AmB aqueous pores plays in triggering signal transduction responses in both pathogens and host immune cells.
-
4.
Is there any barrier impairment in sensitive skin?: a quantitative analysis of sensitive skin by mathematical modeling of transepidermal water loss desorption curves.
Pinto, P, Rosado, C, Parreirão, C, Rodrigues, LM
Skin research and technology : official journal of International Society for Bioengineering and the Skin (ISBS) [and] International Society for Digital Imaging of Skin (ISDIS) [and] International Society for Skin Imaging (ISSI). 2011;(2):181-5
Abstract
BACKGROUND/PURPOSE Sensitive skin is a vague, subjective and difficult to characterize affliction. It affects a large part of the population and is accompanied with great interest by the cosmetic industry. Some studies have suggested that sensitive skin is the result of impaired barrier function, which leads to the exposure of immune system cells and sensitive nerves, resulting in marked cutaneous responses to otherwise harmless stimuli. This study aimed to investigate the cutaneous barrier integrity of individuals with sensitive skin by a novel approach: a plastic occlusion stress test followed by measurement of transepidermal water loss (TEWL) desorption curves. METHODS The study was conducted in volunteers with sensitive skin in the hands and a control group with no sensitivity complaints. A previously developed mathematical model was adjusted to the TEWL data points and two parameters were calculated: dynamic water mass and the evaporation half-life period. RESULTS Statistically significant differences have been detected in the parameters obtained in the sensitive skin group, which supports the thesis that individuals with an increased skin susceptibility have impaired barrier function. CONCLUSION Whereas in the studies based in basal TEWL measurements only discrete differences were reported, the dynamic approach followed in this study provided unequivocal evidence of barrier impairment. The methodology enabled a more objective characterization of sensitive skin and can potentially be applied to the diagnosis/prediction of sensitivity; as well as the efficacy assessment of cosmetic products that are specifically designed to fulfill the needs of consumers with this skin condition.
-
5.
A molecular dynamics study of human defensins HBD-1 and HNP-3 in water.
Sharadadevi, A, Nagaraj, R
Journal of biomolecular structure & dynamics. 2010;(4):541-50
Abstract
Mammalian defensins are crucial components of the innate immune system. They are characterized by three disulfide bridges and exhibit broad spectrum antibacterial activity. The spacing between the cysteines and disulfide connectivities in the two classes of defensins, the alpha- and beta-forms, are different. The structural motif of 3 beta-strands appears to be conserved in alpha- and beta-defensins despite differences in disulfide connectivities and spacing between cysteines. In this study, Molecular Dynamics Simulations (MDS) have been carried out to study the conformational behavior of alpha- andbeta-defensins with and without disulfide bridges. Our results indicate that beta-strands in the C-terminal region of HBD-1 and HNP-3 do not unfold during the course of MDS. The segment adopting alpha-helix in HBD-1 unfolds early during the simulations. The backbone hydrogen bonds in HBD-1 and HNP-3 are broken during MDS. When the disulfide bonds are absent, the N-terminal beta- strand unfolds by 20 ns but beta-strands are observed in the C-terminal region of HNP-3. HBD-1, without disulfide bridges, unfolds to a greater extent during the course of the MDS. Examination of distances between sulfur atoms of cysteines without disulfide bridges during the simulations indicate that there is no specific preference for native disulfide bridges, which could be the reason for the experimental observation of non-native disulfide bridge formation during chemical synthesis of human alpha- and beta-defensins. Since defensins with non-native disulfide bridges are biologically active, the exact three dimensional structures observed for native HBD-1 and HNP-3 does not appear to be essential for exhibiting antibacterial activity.
-
6.
Water content profiles with a 1D centric SPRITE acquisition.
Mastikhin, IV, Mullally, H, MacMillan, B, Balcom, BJ
Journal of magnetic resonance (San Diego, Calif. : 1997). 2002;(1):122-30
Abstract
The purpose of this work is to develop a rapid MRI method amenable to profiling with minimal or no T(1) relaxation weighting. The behavior of a signal during a centric SPRITE acquisition is analyzed. It is shown that the technique can be made immune to a broad range of T(1) changes. In a properly executed measurement, only T(2)* and proton density parameters define the image intensity. A T(2)* mapping technique can be easily applied, separating T(2)* and proton density contributions to the image. A drying soil sample with low initial water content is experimentally studied as a demonstration of the technique. A characteristic baseline artifact is easily removed from the profiles by a simple operation.
-
7.
Low-power water suppression by hyperbolic secant pulses with controlled offsets and delays (WASHCODE).
Starcuk, Z, Starcuk, Z, Mlynárik, V, Roden, M, Horký, J, Moser, E
Journal of magnetic resonance (San Diego, Calif. : 1997). 2001;(1):168-78
Abstract
A class of chemical-shift-selective (CHESS) water suppression (WS) schemes is presented in which the characteristic frequency-domain excitation profiles of "adiabatic" full-passage (AFP) RF pulses are utilized for frequency-selective excitation of the water resonance. In the proposed WS schemes, dubbed WASHCODE, hyperbolic secant (HS) pulses were used as the AFP pulses. Besides the high immunity of WS efficiency toward B(1) inhomogeneity, these sequences also exhibit extraordinary insensitivity to the dispersion of the water T(1) relaxation times. The actual performance of the proposed WS schemes was achieved in particular by optimizing the frequency offsets of WS HS pulses and the time intervals between them. To reduce the RF power requirements of these WS sequences for in vivo applications, HS pulses with the minimum possible frequency bandwidths were employed, which also substantially reduced the adverse effects on the observed proton MR spectra. The proposed WS schemes were evaluated by simulations based on the Bloch equations. Several WS sequences which looked particularly promising were verified experimentally on the human brain on a 3 T MR scanner using very short echo-time STEAM for volume selection and a standard single-loop surface coil for both signal transmission and reception. Routinely, water-suppression factors ranging from 2000 to 4000 were achieved in vivo without additional adjustment of parameters for individual subjects and without violating legal safety limits.